1. Field of the Invention
The present invention generally relates to building constructions and, more particularly, is concerned with a reinforced stucco panel and straw insulator wall assembly.
2. Description of the Prior Art
Straw is the tubular stem of harvested grains, such as wheat, barley, rice and oats. Straw is considered a waste product and in many areas is left in a field and burned. Since the early part of this century, many individuals have attempted to use straw as a source of building material because straw bales have efficient insulating qualities and because straw is so readily available as a waste product. The use of straw is also an environmentally sound alternative to the use of trees as a source of building materials. Straw bales, however, have been used with limited success.
A typical wall section employs a series of horizontally aligned straw bales which are stacked vertically to a certain height and are covered with a coating of stucco mortar, which is comprised of water, lime, cement and sand. The stucco mortar bonds to the straw bale. This coupling reduces the tendency of the stucco to flex as the straw bale coupling effectively increases the overall thickness of the stucco. Tests in laboratories show that straw supports a loading of 2.43 pounds per square inch, whereas stucco has a compressive strength of 2,000 pounds per square inch. Straw alone is easily compressible and therefore limited in its use to load bearing wall systems and limited in wall height to single story buildings. Walls constructed with stucco, however, are semi-rigid and offer little resistance to compression, torque loading or lateral shear.
A failing of past structures is due to moisture that enters the wall from numerous small fractures created by expansion and contraction cycles as the stucco surface is heated and cooled by atmospheric changes. Moisture that passes through the wall causes the straw to collapse and to decompose within the wall and this creates voids that sever the straw-stucco coupling and structurally weaken the wall. Large roof overhangs, which shade the wall and protect it from rain showers, is an accepted means for maintaining structural integrity, but does not eliminate the problem and limits the usefulness of this system of wall construction.
The foundation support for straw bale construction varies considerably from standard construction practices. The standard framed-construction procedures call for a 16-inch wide concrete footing below frost line which supports an 8-inch wide concrete stem wall which in turn supports an above-ground sheeted stud wall. Following this accepted practice where the stem wall provides full width support of the above-ground wall section, straw bale construction would require a minimum 18-inch wide stem wall extending below frost line. Use of monolithic slabs with a perimeter depth of 8 inches and a width of 18 inches or greater accommodates straw bale construction but is limited to use in warm climates where there is no danger of foundation failure which may result from frost heaving. In cold climates, insulation board may be placed radially around a building perimeter just below the soil surface as a means to insulate the soil from severe cold and prevent water from penetrating the soils near the building.
Representative examples of building constructions are disclosed in U.S. Pat. No. 1,604,097 to Hewlett and U.S. Pat. No. 5,398,472 to Eichelkraut. The Hewlett and Eichelkraut patents each disclose the use of straw bales as building blocks. While these and other prior art constructions appear to be satisfactory in use for the specific purposes for which they were designed, it is apparent from the above discussion that a more effective means still needs to be developed in using straw bales and stucco in building construction.